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Modeling Radioelement Dispersion from Fukushima Power Plant: Methodology for an Emergency Response

This study details the methodology for assessing the dispersion of radioelements into the sea from the Fukushima Power Plant, including source estimation, residence time in water and sediment, and monitoring processes. The research involves an ocean model, bathymetry data, tidal forcing, air-sea fluxes, and radionuclide inputs to analyze the impact on the coastal region. Results on radionuclide deposition, liquid release source terms, and residence times inform emergency response strategies.

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Modeling Radioelement Dispersion from Fukushima Power Plant: Methodology for an Emergency Response

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  1. Modeling the Dispersion of Radioelements from the Fukushima Power Plant into the Sea: Methodology for an Emergency Answer, Estimation of Sources, Residence time in the Water Column and Sediment Claude Estournel for the SIROCCO group, CNRS, Univ.Toulouse, France Emmanuel Bosc and Iolanda Osvath, IAEA, Monaco Marc Boquet, Victor Winiarek, CEREA, Paris Tech presented by Patrick Marsaleix

  2. Motivation • Request from IAEA on March 14: dispersion into the sea of radionuclides from the atmosphere and from direct release • Daily conferences with IAEA: data availability, last news… • March 24: (10 days later) first bulletin on the Sirocco website • Regular improvement of the system and the results Material • Sirocco Ocean Model(Marsaleix et al., JAOT 2006, Ocean Modelling 2008, 2009a,b, 2011): free surface, sigma coordinate, curvilinear grid (resolution 600m to 5km) • Bathymetry : Japan Oceanographic Data Center merged with GEBCO-08 30" database • Tidal forcing :

  3. Motivation • Request from IAEA on March 14: dispersion into the sea of radionuclides from the atmosphere and from direct release • Daily conferences with IAEA: data availability, last news… • March 24: (10 days later) first bulletin on the Sirocco website • Regular improvement of the system and the results Material • Sirocco Ocean Model(Marsaleix et al., JAOT 2006, Ocean Modelling 2008, 2009a,b, 2011): free surface, sigma coordinate, curvilinear grid (resolution 600m to 5km) • Bathymetry : Japan Oceanographic Data Center merged with GEBCO-08 30" database • Tidal forcing: T-UGOm (Lyard et al., 2006) Mean tidal transport (a few cm/s) after one year of integration • Air-Sea Fluxes: Bulk formulae (ECMWF air parameters and radiative fluxes) resolution: 3hrs, 0.25°

  4. MERCATOR SST NCOM SST NCOM surf. current MERCATOR surf. current Material (continued) Lateral open boundary conditions and initial state: comparison of two operational models • MERCATOR (French operational model) used for the Sirocco bulletin • NCOM (US Navy operational model) now being tested A higher resolution in MERCATOR Similitudes: the Kuroshyo current Differences: Eddies, alongshore circulation

  5. RADIONUCLIDES INPUT 137 Cs Outputs of the atmosph transport model Polyphemus/Polair3D (1hr, 0.25° resolution) pers. comm. M. Bocquet & V. Winiarek, Ecole des Ponts ParisTech/CEREA 1. Atmospheric deposit Source term (on our domain) Cumulated deposition on the sea: 2.6 1015 Bq

  6. RADIONUCLIDES INPUT 2. Direct liquid release Unknown, an a priori Cesium 137 flux is thus introduced at the coast. Following a simple inverse method (prediction/correction runs), the input flux is deduced from the nearest monitoring stations T1 and T2 (30m & 300m of NPP). Bq/l simulation obs. at 30 and 300m of the NPP NPP

  7. simulation observation 100km ALONGSHORE VALIDATION At 10 and 16 km south of the NPP 2 long series of data Good agreement model/observation Daini Bq/l detection limit Independent observations NPP Iwasawa Bq/l Independent observations e.g. not involved in the calibration of the source term

  8. Bq/l simulation observation 100km VALIDATION at 3km offshore over a ~80km north-south segment Independent observations No observation during the peak of release Independent observations No observation during the peak of release NPP Independent observations No observation during the peak of release

  9. simulation observation 100km Bq/l VALIDATION at 15 km offshore Underestimation of the simulated atmospheric deposit in the northern region ? Independent observations NPP Independent observations

  10. 137 Cs A major result of this study: the source term of the direct liquid release A correct agreement observation/simulation = Confidence in the liquid source term Source term Cumulated release into the sea: 5.6 1015 Bq

  11. RESIDENCE TIME IN THE COASTAL REGION one-monthaverages Bq/l June 1 – June 30 March 20 – April 20 May 1 – May 31 high inputs & strong confinement due to rather calm wind conditions more wind events causing dispersion

  12. RESIDENCE TIME IN THE COASTAL REGION Songda Typhoon Stock of Cesium in the coastal box one-monthaverages June 1 – June 30 March 20 – April 20 May 1 – May 31

  13. ESTIMATION OF DEPOSITION OF CESIUM ON THE SEDIMENT 1.105 1.105 2.104 2.104 1.104 1.104 2.103 2.103 1.103 1.103 2.102 2.102 1.102 1.102 20 20 10 10 2 2 1 1 0.2 0.2 Based on KD=4000liter/kg (IAEA,2004), a concentration of suspended matter of 5mg/l and a sedimentation velocity of ~ 1m/day (very fine suspended matter) Bq/m2 Bq/m2 end of June from the atmosphere from the direct release

  14. Wave height calculated with the Wavewatch3 model Songda Typhoon PERSPECTIVE AT LOCAL SCALE in collaboration with Institut de Radioprotection et de Sûreté Nucléaire (IRSN) through a PhD fellowship (We a looking for a candidate!) • take into account secondary sources • Input by rivers • Resuspension of contaminated sediments

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